Selection of Component Modes for Craig-Bampton Substructure Representations

1996 ◽  
Vol 118 (2) ◽  
pp. 264-270 ◽  
Author(s):  
D. C. Kammer ◽  
M. J. Triller
Keyword(s):  
Efficient Method ◽  
Singular Values ◽  
General Purpose ◽  
Mode Shapes ◽  
Frequency Range ◽  
Reduced Representation ◽  
Absolute Measure ◽  
Fixed Interface ◽  
Interface Mode ◽  
Selection Of

Three measures of modal dynamic importance are studied for the purpose of ranking Craig-Bampton substructure fixed interface mode shapes based upon their contribution to forces at the substructure interface, modal velocity, or modal displacement. These measures can be employed to identify mode shapes which are dynamically important and thus should be retained in a reduced analytical representation, or identified during a modal survey of the substructure. The first method considered. Effective Interface Mass, has been studied previously. However, new results are presented showing the relation between Effective Interface Mass and a commonly used control dynamics measure of modal importance called approximate balanced singular values. In contrast to the general case of approximate balanced singular values, Effective Interface Mass always gives an absolute measure of the dynamic importance of mode shapes. The EIM method is extended to consider modal velocity and modal displacement outputs. All three measures are applied to a simple substructure called the General Purpose Spacecraft. It is shown that each of these measures provides an efficient method for ranking the dynamic importance of Craig-Bampton fixed interface modes such that a reduced representation will accurately reproduce the substructure’s response in the frequency range of interest.

Prediction of Turbomachinery Aeroelastic Behavior From a Set of Representative Modes

2011 ◽  
Author(s):  
Mari´a A. Mayorca ◽  
Damian M. Vogt ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Wide Frequency Range ◽  
Least Square ◽  
Mode Shapes ◽  
Frequency Range ◽  
Reduced Order ◽  
Transonic Compressor ◽  
Unsteady Aerodynamic ◽  
Shape Perturbation ◽  
Selection Of

A method is proposed for the determination of the aeroelastic behavior of a system responding to mode-shapes different to the tuned in-vacuo ones, due to mistuning, mode family interaction or any other source of mode-shape perturbation. The method is based on the generation of a data base of unsteady aerodynamic forces arising from the motion of arbitrary modes and uses Least Square approximations for the prediction of any responding mode. The use of a reduced order technique allows for mistuning analyses and is also applied for the selection of a limited number of arbitrary modes. The application on a transonic compressor blade shows that the method captures well the aeroelastic properties in a wide frequency range. A discussion of the influence of the mode-shapes and frequency on the final stability response is also provided.

Prediction of Turbomachinery Aeroelastic Behavior From a Set of Representative Modes

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
María A. Mayorca ◽  
Damian M. Vogt ◽  
Hans Mårtensson ◽  
Torsten H. Fransson
Keyword(s):  
Wide Frequency Range ◽  
Least Square ◽  
Mode Shapes ◽  
Frequency Range ◽  
Reduced Order ◽  
Transonic Compressor ◽  
Unsteady Aerodynamic ◽  
Shape Perturbation ◽  
Selection Of

A method is proposed for the determination of the aeroelastic behavior of a system responding to mode-shapes which are different from the tuned in vacuo ones, due to mistuning, mode family interaction, or any other source of mode-shape perturbation. The method is based on the generation of a data base of unsteady aerodynamic forces arising from the motion of arbitrary modes and uses least square approximations for the prediction of any responding mode. The use of a reduced order technique allows for mistuning analyses and is also applied for the selection of a limited number of arbitrary modes. The application of this method on a transonic compressor blade shows that the method captures the aeroelastic properties well in a wide frequency range. A discussion of the influence of the mode-shapes and frequency on the final stability response is also provided.

scholarly journals A Multiple and Multi-Level Substructure Method for the Dynamics of Complex Structures

2021 ◽  
Vol 11 (12) ◽  
pp. 5570
Author(s):  
Binbin Wang ◽  
Jingze Liu ◽  
Zhifu Cao ◽  
Dahai Zhang ◽  
Dong Jiang
Keyword(s):  
Structural Characteristics ◽  
Complex Structure ◽  
Complex Structures ◽  
System Matrix ◽  
Substructure Method ◽  
Residual Structure ◽  
The Matrix ◽  
Multi Level ◽  
Fixed Interface ◽  
Selection Of

Based on the fixed interface component mode synthesis, a multiple and multi-level substructure method for the modeling of complex structures is proposed in this paper. Firstly, the residual structure is selected according to the structural characteristics of the assembled complex structure. Secondly, according to the assembly relationship, the parts assembled with the residual structure are divided into a group of substructures, which are named the first-level substructure, the parts assembled with the first-level substructure are divided into a second-level substructure, and consequently the multi-level substructure model is established. Next, the substructures are dynamically condensed and assembled on the boundary of the residual structure. Finally, the substructure system matrix, which is replicated from the matrix of repeated physical geometry, is obtained by preserving the main modes and the constrained modes and the system matrix of the last level of the substructure is assembled to the upper level of the substructure, one level up, until it is assembled in the residual structure. In this paper, an assembly structure with three panels and a gear box is adopted to verify the method by simulation and a rotor is used to experimentally verify the method. The results show that the proposed multiple and multi-level substructure modeling method is not unique to the selection of residual structures, and different classification methods do not affect the calculation accuracy. The selection of 50% external nodes can further improve the analysis efficiency while ensuring the calculation accuracy.

scholarly journals Principled approach to the selection of the embedding dimension of networks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weiwei Gu ◽  
Aditya Tandon ◽  
Yong-Yeol Ahn ◽  
Filippo Radicchi
Keyword(s):  
Real World ◽  
Structural Information ◽  
General Purpose ◽  
Embedding Dimension ◽  
Network Embedding ◽  
Machine Learning Technique ◽  
Learning Technique ◽  
Low Dimensional ◽  
Large Corpus ◽  
Selection Of

AbstractNetwork embedding is a general-purpose machine learning technique that encodes network structure in vector spaces with tunable dimension. Choosing an appropriate embedding dimension – small enough to be efficient and large enough to be effective – is challenging but necessary to generate embeddings applicable to a multitude of tasks. Existing strategies for the selection of the embedding dimension rely on performance maximization in downstream tasks. Here, we propose a principled method such that all structural information of a network is parsimoniously encoded. The method is validated on various embedding algorithms and a large corpus of real-world networks. The embedding dimension selected by our method in real-world networks suggest that efficient encoding in low-dimensional spaces is usually possible.

Selection of Degrees of Freedom for Dynamic Analysis

1987 ◽  
Vol 109 (1) ◽  
pp. 65-69 ◽  
Author(s):  
K. W. Matta
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
General Purpose ◽  
Component Mode Synthesis ◽  
Complex Structures ◽  
Large Complex ◽  
Static Condensation ◽  
Basis Vectors ◽  
Selection Of

A technique for the selection of dynamic degrees of freedom (DDOF) of large, complex structures for dynamic analysis is described and the formulation of Ritz basis vectors for static condensation and component mode synthesis is presented. Generally, the selection of DDOF is left to the judgment of engineers. For large, complex structures, however, a danger of poor or improper selection of DDOF exists. An improper selection may result in singularity of the eigenvalue problem, or in missing some of the lower frequencies. This technique can be used to select the DDOF to reduce the size of large eigenproblems and to select the DDOF to eliminate the singularities of the assembled eigenproblem of component mode synthesis. The execution of this technique is discussed in this paper. Examples are given for using this technique in conjunction with a general purpose finite element computer program GENSAM[1].

Book Reviews

2000 ◽  
Vol 38 (1) ◽  
pp. 115-165 ◽  
Keyword(s):  
English Language ◽  
Value Added ◽  
General Purpose ◽  
Original Research ◽  
Book Selection ◽  
Economic Association ◽  
Single Well ◽  
Selection Of ◽  
Made In

Editor's Note: Guidelines for Selecting Books to Review Occasionally, we receive questions regarding the selection of books reviewed in the Journal of Economic Literature. A statement of our guidelines for book selection might be useful, therefore. The general purpose of our book reviews is to help keep members of the American Economic Association informed of significant English-language publications in economics research. Annotations are published of all books received. However, we receive many more books than we are able to review so choices must be made in selecting books for review. We try to identify for review scholarly, well-researched books that embody serious and original research on a particular topic. We do not review textbooks. Other things equal, we avoid volumes of collected papers such as festschriften and conference volumes. Often such volumes pose difficult problems for the reviewer who may find himself having to describe and evaluate many different contributions. Among such volumes, we prefer those on a single, well-defined theme that a typical reviewer may develop in his review. A volume that collects together papers from a wide assortment of different topics is not preferred to one devoted exclusively to one topic. We avoid volumes that collect previously published papers unless there is some material value added from bringing the papers together. Also, we refrain from reviewing second or revised editions unless the revisions of the original edition are really substantial. Our policy is not to accept offers to review (and unsolicited reviews of) particular books. We have examined the consequences of an alternative policy and have determined that we lack the resources to deal appropriately with unsolicited reviews. Coauthorship of reviews is not forbidden but discouraged and we ask our invited reviewers to discuss with us first any changes in the authorship or assigned length of a review. [Reprinted from JEL, March 1992, 30(1), p. vi.]

scholarly journals Pre-selection of the candidate fields for deep imaging of the epoch of reionization with SKA1-low

2020 ◽  
Vol 499 (3) ◽  
pp. 3434-3444
Author(s):  
Qian Zheng ◽  
Xiang-Ping Wu ◽  
Quan Guo ◽  
Melanie Johnston-Hollitt ◽  
Huanyuan Shan ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Low Frequency ◽  
Far Field ◽  
Frequency Range ◽  
High Quality ◽  
Average Surface ◽  
Square Kilometre Array ◽  
Broad Frequency Range ◽  
Deep Imaging ◽  
Selection Of

ABSTRACT The Square Kilometre Array (SKA) will be the first low-frequency instrument with the capability to directly image the structures of the epoch of reionization (EoR). Indeed, deep imaging of the EoR over five targeted fields of 20 sq deg each has been selected as the highest priority science objective for SKA1. Aiming at preparing for this highly challenging observation, we perform an extensive pre-selection of the ‘quietest’ and ‘cleanest’ candidate fields in the southern sky to be suited for deep imaging of the EoR using existing catalogues and observations over a broad frequency range. The candidate fields should meet a number of strict criteria to avoid contaminations from foreground structures and sources. The candidate fields should also exhibit both the lowest average surface brightness and smallest variance to ensure uniformity and high-quality deep imaging over the fields. Our selection eventually yields a sample of 7 ‘ideal’ fields of 20 sq deg in the southern sky that could be targeted for deep imaging of the EoR. Finally, these selected fields are convolved with the synthesized beam of SKA1-low stations to ensure that the effect of sidelobes from the far-field bright sources is also weak.

Book Reviews

2005 ◽  
Vol 43 (4) ◽  
pp. 1063-1086
Keyword(s):  
English Language ◽  
Value Added ◽  
General Purpose ◽  
Original Research ◽  
Book Selection ◽  
The Public ◽  
Economic Association ◽  
Single Well ◽  
Selection Of

Occasionally, we receive questions regarding the selection of books reviewed in the Journal of Economic Literature. A statement of our guidelines for book selection might therefore be useful. The general purpose of our book reviews is to help keep members of the American Economic Association informed of significant English-language publications in economics research. We also review significant books in related social sciences that might be of special interest to economists. On occasion, we review books that are written for the public at large if these books speak to issues that are of interest to economists. Finally, we review some reports or publications that have significant policy impact. Annotations are published for all books received. However, we receive many more books than we are able to review so choices must be made in selecting books for review. We try to identify for review scholarly, well-researched books that embody serious and original research on a particular topic. We do not review textbooks. Other things being equal, we avoid volumes of collected papers such as festschriften and conference volumes. Often such volumes pose difficult problems for the reviewer who may find herself having to describe and evaluate many different contributions. Among such volumes, we prefer those on a single, well-defined theme that a typical reviewer may develop in his review. We avoid volumes that collect previously published papers unless there is some material value added from bringing the papers together. Also, we refrain from reviewing second or revised editions unless the revisions of the original edition are really substantial. Our policy is not to accept offers to review (and unsolicited reviews of) particular books. Coauthorship of reviews is not forbidden but it is unusual and we ask our invited reviewers to discuss with us first any changes in the authorship or assigned length of a review.

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